The present invention relates to a pressure-control valve. More particularly this invention concerns a two-way pressure limiting valve.
It is frequently necessary, in a shock absorber or the like, to limit the pressure differential existing between two lines. A two-way pressure-control valve is employed which connects the two lines together whenever the pressure in either of the lines exceeds the pressure in the other line by a predetermined differential.
Such a valve is known whose housing is formed with an axis-defining bore into which open two axially spaced ports each of which is connected to a respective one of the above-mentioned lines. Slidable in one position against the force of a biasing spring from a predetermined central rest position is a sleeve. A valve body is slidable in the opposite direction from a central rest position against the force of a spring also. In the central rest positions the valve body and the sleeve lie snugly against each other and prevent flow between the ports. When the one line is pressurized to a predetermined extent more than the other line the sleeve will be pushed away from the valve body and, therefore, the ports will be connected. When the other port is pressurized to a predetermined extent more than the one port the valve body is pushed away from the sleeve and, once again, the two ports are interconnected.
Such a valve is relatively expensive to manufacture and complicated in use. In addition the effective surface areas of the two members, namely the valve body and the seat-forming sleeve, are different so that the pressure differential for response in one direction is different from the pressure differential in the other direction. What is more the use of a valve body and sleeve of this type often allows considerable leakage through the system when it is not responding to a pressure differential.